Distance indicator for telescopes



June 22, 1937. c. F. DREW, JR

DISTANCE INDICATOR FOR TELESCOPES Filed Nov. 26, 1935 INVEITIO www MN:QN.. ww S @WH .JW M .WN m. m w y@ EEE v @.Nmw. MM. NNl

Patented June 22, 1937 UNITED STATES PATENT OFEICE 4 Claims.

yi() in surveying, particularly in stadia measurements, it has beennecessary to send 'out a rodman withv a stadia rod to the point, thedistance of which is to be determined.

I have invented an attachment for telescopes "r .which indicatesdirectly the distance from the telescope to the object on which it isfocused. This device greatly facilitates the measurement 'of distancesnot only in the eld of surveying and stadia measurements, but also inrange nding and astronomical observations. In accordance with myinvention, I provide the telescope with movable indicating meansactuated by the mechanism which is ordinarily used to adjust the focusof the telescope, The mechanism may take any convenient form, but inthat to be described in detail herein, it comprises a movable vscale anda movable pointer geared to the focusing means, i. e., the objectiveadjusting shaft. While the invention will be described as applied to asurveyors transit, it will be apparent that it may be incorporated inany telescope which is focused by adjusting the relative positions ofthe eye-piece and objective.

A preferred form of the invention is illustrated in the accompanyingdrawing, although it will be apparent that the invention may beotherwise embodied Within the scope of my broader claims.

In the drawing:

Figure 1 is a partial plan view of a surveyors transit having theinvention embodied therein,

parts being shown in section;

Figure 2 is a transverse sectional view along the line II-II of Fig. 1;

Figure 3 is a similar view along the line III- III of Fig. 1; and

Figure 4 is a partial longitudinal section along the line IV--IV of Fig.1.

Referring now in detail to the drawing, a transit telescope I0 issupported on trunnions II providing a horizontal axis of rotation. Anobjective cell I2ris slidably supported on an objective slide or tube i3reciprocable in the tube I0. A dust guard tube I4 extends rearwardly ofthe 55 objective cell I2 on the outside of the main tube I0. Theeye-piece is mounted at the end of the tube I0 opposite the objectivecell I2, in the usual manner.

A rack bar I5 is secured to the inside of the objective slide I3 and isadapted to be engaged by a pinion I6. The pinion i5 is secured to ashaft I'i journaled vertically in a bearing I3 mounted on the main tubeIIB. At the upper end of the shaft I'I a knurled wheel I9 is provided topermit manual adjustment of the slide I3 in the tube i i! for focusingthe telescope.

The shaft Il is also provided with a gear 2G. The gear iii meshes with apinion 2l secured to a shaft 22. The shaft 22 is journaled in bearings23 mounted on the tube Ii) in the same manner as the bearing i8. Theshaft 22 is also provided with a gear 24 meshing with pinions 25. and25. These pinions are secured on shafts 2! and 2S journaled in bearings29 and 3B. The shafts 2l' and 28 are also provided with pinions 3l and32.

The pinion 3i meshes with rack teeth formed on a pointer slide 33movable in guides 34 longitudinally of the telescope. Similarly, a slide35 having a graduated scale 36 thereon is movable in longitudinal guides31. The slide 33 carries a pointer or index 38 cooperating With thegraduated scale on the slide 35, and has rack teeth in mesh with thepinion 32. The mechanism a1- ready described is enclosed in a housing 39and may, if desired, be made detachable as a unit from the telescope.The housing 39 has a Window 40 therein provided with a magnifying lens4I through which the relative positions of the index and scale may beobserved, and a reading taken.

It will be apparent from the description given thus far that operationof the shaft I'I by means of the wheel I9, to effect a focusingadjustment oitthe objective, will cause an increased, thoughproportional, movement of the slides 33 and 35 and that these slidesWill move in opposite directions, as indicated by the arrows in Fig. 1`In accordance with well-known optical laws, the distance between theobjective and the eye-piece bears a definite relation to the distancefrom the telescope to the object on which it is focused. The scale 36may therefore be graduated in any suitable units, whereby the distancefrom the telescope to an object on which it is focused may be determinedby noting the position of the index 38 relative to the scale 36. The useof multiplying gears between the focus-adjusting means and theindicating slides and the considerable length of the scale 36 provide anaccuracy of measurement which is suicient for many purposes, comparingfavorably, for example, with vll) the accuracy of stadia measurements.The scale 35, it will be noted, is not uniform. Greater accuracy,therefore, is obtainable for short distances than for long distances,but measurements may be madey to within about one foot, even atdistances of approximately 1000 feet, so that the percentage of error isvery small.

The advantages of the invention described will be obvious immediately.Among them' may be mentioned the great increase in the speed at whichmeasurements may be made for map making, contour work, and the like,since the services oi a rodman are dispensed with altogether, and theonly delay involved in making an observation, represented by the timenecessary to focus the telescope. Applications of the invention otherthan to the art of surveying will readily suggest themselves, such asrange finding, astronomical work, and the like. While the invention hasbeen specifically described herein as embodied in the telescope of asurveyors transit, it will be understood that the specic structuredisclosed is merely by way of example and not a limitation upon theinvention. Other specific forms of the device may, of course, beresorted to Without departing from the spirit of the invention or thescope of the appended claims.

I claim:

l. A telescope comprising a tube, an objective cell reciprocabletherein, means for manually reciprocating the cell in the tube, agraduated scale slidable on said tube, a pointer bar also slidable onsaid tube and having a pointer adapted to cooperate with said scale, andmultiplying gearing for actuating said pointer bar and scale in oppositedirections, said gearing being driven by said means.

2. A telescope comprising `a tube, an objective cell reciprocabletherein, a shaft journaled in said tube, means whereby rotation of saidshaft effects adjustment of the cell relative to the tube to focus thetelescope, a graduated scale slidable along said tube, a bar .alsoslidable along the tube and having a pointer cooperating with saidscale, said bar and scale having rack teeth thereon, shafts rotatablymounted on said tube having pinions thereon meshing with said rackteeth, and multiplying gearing between said last-mentioned shafts andsaid first-mentioned shaft.

3. A telescope comprising a tube, an objective cell reciprocabletherein, means including a rotatable shaft for reciprocating the cell inthe tube, a graduated scale movably mounted on said tube, a pointer baralso movable on the tube and adapted to cooperate with said scale, rackteeth on said bar and scale, shafts journaled in the tube having pinionsthereon meshing with said teeth, and multiplying gearing between saidlast-mentioned shafts and said first-mentioned shaft.

4f. In a telescope comprising a tube, an objective cell reciprocabletherein, a scale slidable along said tube, a pointer bar also slidablealong the tube and having a pointer adapted to cooperate With saidscale, a shaft rotatably mounted on the tube for adjusting the cellrelative to the tube, rack teeth on said scale and pointer bar, shaftsrotatably mounted on the tube having pinions meshing with said teeth,and gearing between said last-mentioned shafts and Said firstmentionedshaft.

CHARLES F. DREW, JR.

